Many attempts have been made to provide filtration systems for the purification and maintenance of suitable aquaria environments, whether of a salt water or fresh water nature. Since an aquarium contains a fixed volume of water, which is used over and over again, its ecology is fragile and dependent upon many interrelated biological vectors.
An aquarium will not function in a proper manner (i.e., it will not present aquarium specimens with a healthful living environment) without a balanced interplay of certain biological and biochemical systems:
A. Oxygen-Carbon Dioxide Cycle: These gases are fundamental in the sustenance of plant and animal life. Plants absorb carbon dioxide which is necessary for photosynthesis and release oxygen for use in animal respiration which also releases carbon dioxide for plant use. It is therefore important, in an aquarium, that there is provided means whereby there is an oxygen/carbon dioxide exchange for the sustenance of said specimens.
B. Nitrogen Cycle: The excreta of aquatic specimens is principally in the form of insoluble organic and inorganic waste matter and urea. The urea is converted to soluble ammonium salts and carbon dioxide in water. Nitrifying bacteria, i.e. nitrococci and nitrate forming bacteria, combined with chemical reaction, oxidize the ammonia to nitrites (which are toxic to aquatic specimens) and then bacterial action oxidizes the nitrites to nitrates which are utilized by plant life and which, in turn, are used as a food source by the aquatic specimens.
C. Particulate Matter: The insoluble organic and inorganic waste materials, which are excreted by aquatic specimens and which also are formed by the natural decomposition of plant and animal tissues, must be removed from the aquarium environment. Soluble particulate matter is converted by bacterial action to plant and animal foods but the concentration of such material in a fixed volume of water, such as an aquarium, must be kept carefully balanced so that the system does not become overloaded.
Although the use of proper aquatic plants combined with natural bacterial action and proper mechanical filtration can provide a relatively balanced system with proper maintenance, the problem of maintaining a proper environment for aquatic specimens in the absence of plant materials has recently become more important. This problem is important to those professionals and hobbyists who do not or cannot provide the time necessary to adequately maintain a flourishing plant colony within the aquarium and it has become especially important for those professionals and hobbyists who prefer to maintain marine specimens. The maintenance of a proper plant colony in a salt water aquarium is much greater than that required to maintain a plant colony in a fresh water aquarium. Further, it is preferred, many times, to exclude plant material from the aquarium, even those aquariums utilizing fresh water, since it is difficult to keep the aquarium clean due to the decomposition of plant material. Resort must be had to vacuum cleaning of the aquarium and periodically replacing the aquarium water in order to prevent the water from becoming overloaded with decomposing plant material to the detriment of marine or fresh water specimens. The use of particulate filters, such as are known and which utilize carbon and/or fibrous materials, does not provide sufficient filtration action to provide a healthful environment for aquatic specimens.